Capacitive sensor on a transparent carrier

ABSTRACT

In a capacitive sensor on at least one carrier ( 2, 4 ) made of transparent material, e. g. glass, it is provided that the transparent carrier ( 2,4 ) comprises an electrically conducting transparent layer ( 6,10 ) which serves as a transparent sensor surface.

BACKGROUND OF THE INVENTION

The invention relates to a capacitive sensor.

Such sensors can be used on glass surfaces on which switching functionsare to be performed.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a capacitive sensor whichallows an approach to said sensor to be sensed on a carrier oftransparent material, e. g. glass. Another object is to perform alocalization of the approach.

The invention advantageously provides for the transparent carriermaterial to comprise an electrically conducting layer which serves as atransparent sensor surface.

The electrically conducting layer comprises terminal lines.

The electrically conducting layer can be capacitively and contactlesslycoupled into an electrical field of a second sensor surface which isprovided in the vicinity in an immediately connected relationship.

The electrically conducting layer can be subdivided by incorporatedinsulation paths into different portions, wherein independent capacitivesensors are connected to each separate sensor surface. Due to thesubdivision by the insulation paths line-type sensor paths are formed.

Between the sensor surfaces narrow separating surfaces may be arrangedwhich are grounded so as to be neutral.

Each electrically conducting layer may be coated with a transparentscratch-resistant insulating layer.

The carrier may be made of tempered glass or compound glass.

In a preferred embodiment a plurality of electrically conductingtransparent layers are provided whose capacitive functions penetrateeach other.

Further, a plurality of transparent carriers each having an electricallyconducting layer may be placed one upon the other.

According to another alternative it is provided that a singletransparent carrier comprises a plurality of electrically conductingtransparent layers placed one upon the other, said layers been separatedby insulating intermediate layers.

Hereunder embodiments of the invention are explained in detail withreference to the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first capacitive sensor with diagonally extendingelectrically conducting transparent layers (sensor lines),

FIG. 2 shows a second transparent carrier with transparent electricallyconducting layers extending in opposite direction,

FIG. 3 shows an embodiment of a capacitive complete sensor forlocalization of a contact, and

FIG. 4 shows an embodiment of a capacitive sensor with island-likenonactive surfaces.

The functional principle is based upon a transparent carrier material(e. g. glass) being coated with a transparent conducting material (e. g.indium tin oxide—ITO coating). This conducting coating is electricallycontacted and serves as a transparent sensor surface for a capacitiveproximity switch.

Contacting may be effected in the form of direct contacting by means ofsoldering or glueing to glass, heat-seal technique, conducting adhesivestrips, coatings capable of being soldered, silver printing, or thelike. Further, electrical contacting of the sensor surface can beeffected in a contactless manner by capacitively coupling the coatinginto an electrical field of a sensor surface located in the vicinity indirectly connected relationship. This can be effected by recalibrationof the original sensor surface and can be carried out during operationof an electronic circuit.

Localization of an approach of e. g. a hand to the sensor surface isrealized by subdividing the conducting transparent coating byincorporated insulation paths 11 Into different portions and connectingindependent capacitive sensors to each separate sensor surface. Fordefinite separation and prevention of mutual coupling-in a relativelynarrow separation surface may remain between two sensor surfaces, whichseparation surface is grounded so as to be neutral, if necessary.

A capacitive glass sensor applying the aforementioned functionalprinciple can be constructed in two ways:

1. The construction can be effected on a single transparent glasscarrier 2 which performs the function and may be combined with furtherglass panes, pockets between glass panes and/or backings to form an endproduct. The carrier 2,4 of a transparent sensor surface may also bemade of tempered glass or compound glass.

The conducting coating and the transparent carrier material areconsidered to be a single-layer circuit board, and accordingly theindividual sensor surfaces 6,10 are worked out of the conductingcoating.

All sensor surfaces 6,10 always extend parallel to each other.

A final transparent coating of a scratch-resistant and insulatingmaterial, e. g. aluminium oxide, prevents the conducting layers frombeing damaged.

2. The functional principle of the single-layer configuration can belinked by combination of a plurality of single layers such that notevery sensor surface requires an individual capacitive electronicsensor, but a line and column array minimizes the amount of electronics.Each line and each column is provided with its own capacitive sensorwhich reduces e .g. the amount of electronics for 16 keys in a 4×4matrix to eight capacitive sensors. Further, the amount of contacting onthe transparent sensor surface is reduced.

It is of importance with regard to the localization process that thecapacitive functions of different sensor surfaces (on the differentplanes) penetrate each other and create an invisible commonthree-dimensional functional space.

The various active planes of the sensor surfaces can be produced bymeans of different processes, e. g.:

a) by placing one upon the other a plurality of transparent carriers 2,4with conducting coatings according to the principle described under 1.,or

b) by coating a transparent layer 2,4 several times with a conductingtransparent material, using an insulating intermediate coating, ifnecessary.

When the construction according to variant a) is employed, amultilayered and extremely stable compound glass can be produced e. g.using glass as the carrier material, where the conducting sensorsurfaces are located on the inside of the glass and are thus completelyscratch-resistant and arranged such that any direct access to the sensorsurfaces is prevented. The capacitively active field thus works throughthe material thickness of the glass. The two transparent carriers 2,4made of glass can be connected with each other in different ways: byapplying the compound glass technique using a PVB film, theencapsulating technique using a transparent encapsulating material, theinsulating glass technique using an air gap, loosely placed one upon theother, or adhered to each other by a suitable adhesive. Any screenprinting between the transparent layers may be opaque, translucentand/or partly applied. Between or behind the glass panes the transparentsensor may be connected with a functional layer which allows changeabletransmission of the overall setup.

When a plurality of conducting layers are used on a transparent carrier2,4, the aforementioned setup possibilities apply mutatis mutandis.Generally, the conducting layer of the first sensor surface is appliedfirst and then subdivided into a plurality of sensor surfaces 8,12 orsensor paths according to requirement. Subsequently, an insulatingtransparent coating is applied on which, during the third working cycle,a second electrically conducting layer forms the next sensor surface.The latter can also be subdivided. At option further layers may followwhich can be protected by a final insulating coating on the surface, ifnecessary.

For the sake of simplicity only the construction with two separatecarrier materials is described below:

In the first carrier 2 diagonally extending active capacitive sensorsare formed whose active surfaces have regular enlarged portions in theform of enlargements 8,12 at which this diagonal sensor path 6,10 isparticularly sensitive and has a more strongly active capacitive field.Thus an irregular capacitive full-face sensor has already been formed.Each diagonal sensor path 6,10 is connected to its own capacitivesensor.

Here, each hatched area forms a coherent active surface 6,10, whichsurfaces are defined in the remaining surface of the conducting coatingby an insulation path 11. The longer diagonals are the terminal lines7,9 to the connecting cable, which terminal lines are centrally mergedfor each glass. The diagonals are to be made as narrow as possiblebetween the enlargements 8,12; in the drawings they are shownsuperproportionally enlarged.

In the second carrier 4, too, sensors are formed, but turned by 90 insuch a way that the enlargements 8,12 of both sensor planes supplementeach other to form a full-face pattern.

If these two sensor planes are placed one upon the other in a preciselyfitting manner, a capacitive complete sensor is created which allows,via evaluation of the diagonal columns and diagonal lines on thecarriers 2,4, localization of the contact.

An approach in a crossing point is now ideally sensed by two capacitiveplanar enlargements 8 in a diagonal line and two capacitive planarenlargements 12 in a diagonal column. Via the evaluation of line andcolumn signals the position is obtained.

The enlargements 8 of the rear carrier 2 are located behind a nonactivesurface of the front carrier 4. To allow active detection of an approachwithout any electrical screening by the nonactive layer located infront, this nonactive surface of the front carrier 4 can be coupled intoa capacitive field and can practially be used, too. This is, however, tobe possible only locally over the respective rear carrier 2 enlargementcurrently In use. Therefore the nonactive surface of the front carrier 4(between the diagonal columns) is divided into islands 16 which can becoupled into the enlargements 8 of the rear carrier 2. Further, amarginal area is provided about each island 16, which marginal area isconnected to mass. In this way coupling of the islands 16 into theenlargements of the same sensor plane is prevented.

FIG. 1 shows the active diagonal lines of a carrier 2 with enlargements8.

The octagons in the embodiment of FIG. 4 shows islands 16 between theactive lines, which islands can be coupled into the enlargements lyingbehind them In the next carrier 2.

The intermediate space between the islands 16 and the electricallyconducting layers 10 is grounded.

To allow a multilayer carrier (e. g. compound glass) to be operated fromboth sides, the second carrier has the same construction, i. e. it alsopossesses islands 16 and a grounded intermediate space.

Besides the known advantages of a glass surface (scratch resistance,resistance to acid, alkaline solutions, oils, greases, UV-resistance,option of antireflection coating) the capacitive glass sensor offersfurther advantages owing to its specific construction:

in a compound glass construction contacting can simply be effectedthrough a hole bored into the rear glass pane without the stabilitybeing substantially affected;

the electronic switching system is always relay-controlled and can thusbe used for direct power-switching;

it is possible to install the sensor surface flush with a front plate;

curved, bent, bored and free glass forms are possible;

wear-resisting operating surface;

resistant to vandalism;

splinterproof due to compound glass construction;

increased resistance to shock due to tempering of the glass;

the sensor can be produced with free glass edges all around;

contacting of the sensor surface can be attained by simply placing thecoupling-in sources.

The capacitive glass sensor can e. g. be used in glass panes of a motorvehicle. It can further be used in glass panes of a shower cabinet. Theglass sensor can further be provided on its rear side with an exciterfor transmission of acoustical information.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined by the appended claims.

I claim:
 1. A capacitive sensor comprising at least one carrier (2, 4)made of transparent material, said at least one transparent materialcarrier (2,4) including a plurality of electrically conductingtransparent layers (6, 10) defining a transparent sensor surface, saidplurality of electrically conducting transparent layers (6, 10)establish capacitive functions which penetrate each other, saidplurality of electrically conducting transparent layers extenddiagonally, and two sensor surfaces lying one upon the other establishpath-type electrically conducting layers (6, 10) diagonally extending inopposite directions.
 2. A capacitive sensor comprising at least onecarrier (2, 4) made of transparent material, said at least onetransparent material carrier (2, 4) Including an electrically conductingtransparent layer (6, 10) defining a transparent sensor surface, saidelectrically conducting transparent layers (6, 10) being subdivided by aplurality of insulation paths (11) into separate sensor surfaces,independent capacitive sensors being connected to each separate sensorsurface, and said electrically conducting transparent layer (6, 10)includes enlargements (8, 12).
 3. The capacitive sensor as defined inclaim 2 wherein the electrically conducting transparent layers (6, 10)of neighbouring sensor surfaces cross each other between respectiveenlargements (8, 12).
 4. A capacitive sensor comprising at least onecarrier (2, 4) made of transparent material, said at least onetransparent material carrier (2,4) including a plurality of electricallyconducting transparent layers (6, 10) defining a transparent sensorsurface, said plurality of electrically conducting transparent layersextend diagonally, and two sensors lying one upon the other establishpath-type electrically conducting layers (6, 10) diagonally extending inopposite directions.
 5. A capacitive sensor comprising at least onecarrier (2, 4) made of transparent material, said at least onetransparent material carrier (2, 4) including an electrically conductingtransparent layer (6, 10) defining a transparent sensor surface, andsaid electrically conducting transparent layer (6, 10) includesenlargements (8, 12).
 6. The capacitive sensor as defined in claim 5wherein electrically conducting transparent layers (6, 10) ofneighbouring sensor surfaces cross each other between respectiveenlargements (8, 12).